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Old 12-02-2011, 07:59   #1
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Navigating the 'Old Way'. . .

Doing it the Old way...
Before there were GPS, Loran, and RDF. On overcast days we went by the shaft revolutions at end of watch for distance covered. They still haven't developed a Cloud Splitter for the Sextant... Dang it!!

Rev. X Prop pitch X slippage / 6080 = distance.

Use to do this when I sailed with Military Sealift Command on their ships. You'll be surprised on how close that distance was to Celestial, Pilotage and today's electronics. Many times it was right on top of my DR/fix. There are varilance of that formula for determining; Slippage, RPMs needed for desired speed and so forth.

I know that our "Modern" boats don't have shaft counters... But maybe we should!? Many of my "old" skills has keep me out of trouble many times. Where depending on Today's GPS has shown to be a tad off by several hundred yards.

So I will stick to Coastal Piloting, Celestial and challenge the GPS and see if we both agree... Have know a few Mates & Masters of yesteryears who have DR across the Pacific and arrived right where they were aiming for and as scheduled. Using shaft revolutions and speed run on a course to the next turn.
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Old 14-02-2011, 04:07   #2
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Sometimes, on ECDIS courses, I have to explain that old fashion navigation includes a view through the window. It sound crazy but it is the scary reality.

DR is important even when or if using GPS. I would never trust the GPS as a standalone tool to fix my position and I know that experienced mariner would do that neither.

So, I am convince you will confirm that old fashion navigation works.
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Old 14-02-2011, 04:45   #3
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Of course, "the old way" is a relative term. If old enough, it would include a bag of rocks on the bow for sailing up the foggy fjords. Sling a rock and listen for the splash or the thud!
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Old 14-02-2011, 05:06   #4
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I always have been taught that navigation is the art of verifying where you think you are...by whatever means necessary or available..new or old.

In the last 5 years...I've never had GPS position me more than a few feet off...that doesn't mean that most charts are very accurate...I usually compare to satellite images if there's a discrepancy.

Many cruisers forget to use the lowly depthsounder for coastal cruising...I have seen a few rescue cases where the depthsounder could have saved lives and property.

I'm not sureshaft revs would wok on many small boats...but all the tricks on DR nav should be tools in the NAV bag in case the GPS/chartplotter goes and be used as backup to verify the GPS through better situational awareness.
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Old 14-02-2011, 07:02   #5
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I am reminded of this passage from Joshua Slocum's "Sailing Alone Around the World". Slocum, you may remember, accomplished that feat without a chronometer, so he never knew his longitude except by dead reckoning.

In the log for July 18 there is this entry: "Fine weather, wind south-southwest. Porpoises gamboling all about. The S. S. Olympia passed at 11:30 A. M., long. W. 34 degrees 50'."

"It lacks now three minutes of the half-hour," shouted the captain, as he gave me the longitude and the time. I admired the businesslike air of the Olympia; but I have the feeling still that the captain was just a little too precise in his reckoning. That may be all well enough, however, where there is plenty of sea-room. But over-confidence, I believe, was the cause of the disaster to the liner Atlantic, and many more like her. The captain knew too well where he was. There were no porpoises at all skipping along with the Olympia! Porpoises always prefer sailing-ships. The captain was a young man, I observed, and had before him, I hope, a good record.
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Old 14-02-2011, 07:39   #6
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...Slocum ...never knew his longitude except by dead reckoning.

Slocum says in his book he used Lunar Distance navigation, which can be used to find longitude without a chronometer.

http://en.wikipedia.org/wiki/Lunar_distance_%28navigation%29

EXCERPT:
In celestial navigation, lunar distance is the angle between the Moon and another celestial body. A navigator can use a lunar distance (also called a lunar) and a nautical almanac to calculate Greenwich time. The navigator can then determine longitude without a marine chronometer.
---------------------------

I look forward to having the months at sea it will likely take me to figure out how to do some of the more esoteric forms of celestial navigation.
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Old 14-02-2011, 08:25   #7
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As I recall, he accomplished the lunar angle computations once, while looking for the Marquesas. He must have been powerfully lost and powerfully bored.
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Old 14-02-2011, 09:36   #8
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As I recall, he accomplished the lunar angle computations once, while looking for the Marquesas. He must have been powerfully lost and powerfully bored.
I don't remember reading where Slocum indicated he used lunar distances on only one occasion, as you imply.

In fact, he states "the work of the lunarian, though seldom practised in these days of chronometers, is beautifully edifying, and there is nothing in the realm of navigation that lifts one’s heart up more in adoration." He apparently did not share your view that it was only for the "bored". (And after all, only the boring can be bored - for if one does not possess the wherewithal to entertain even one's own self...)

Slocum had obvious mastery of a wide range of things nautical. His tendency was to make light of many of the skills he possessed and applied during his voyages. These observations, if taken with his sentiment toward lunar distances, as well as his repeated and rather humorously flippant attitude toward his timepiece, seem to possibly suggest that he used lunar distances to find his longitude rather more often than you allow.

He does clearly state that he figured his longitude mostly by "intuition", ded. reckoning and the use of his towed log. But it also seems reasonable to think that on a voyage of that length, considering the importance of knowing one's position, his ability to do it, and the obvious pleasure it gave him, that he used lunar distances on many occasions rather than just the once.
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Old 14-02-2011, 13:58   #9
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Thank you for spelling it "ded. reckoning". I know that "dead reckoning" is not correct, but I use it to avoid explaining the real term time and time again.

Of course, I use "abaft" and "athwart" in my normal, and not Hollywood Pirate, voice, as well.

I save that for "y'arrrrrrrr".
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Old 14-02-2011, 16:00   #10
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Thank you for spelling it "ded. reckoning". I know that "dead reckoning" is not correct, but I use it to avoid explaining the real term time and time again.

Of course, I use "abaft" and "athwart" in my normal, and not Hollywood Pirate, voice, as well.

I save that for "y'arrrrrrrr".
I am all for precise speach.

Interestingly enough, though, the move to "ded. reckoning" appears to be relatively recent. Back in the 1600s, it was called "dead reckoning". The first mention of "ded. reckoning" appears to have been in the 1930s.

The articles below say only one dictionary mentions "ded". All the others leave it as "dead", and a few give what they think are explanations as to why. Dead as in "dead right", "dead slow", etc.

Here are two of the better links I found:

-->World Wide Words: Dead reckoning

-->The Straight Dope: Is "dead reckoning" short for "deduced reckoning"?

Now, languages change fast, so if the term "ded" has been in use for 50+ years, that's long enough to make it valid in it's own right. But given the history, I think "dead reckoning" is also has its claim to validity.

In the end, I don't really care which is used. Not really important. The communication of ideas is what's important.

However, as an intellectual discussion, I love to dig these things up. So this is absolutely NOT to say someone is right/wrong, but just to bring up some interesting history.

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Old 14-02-2011, 16:03   #11
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Thank you for spelling it "ded. reckoning". I know that "dead reckoning" is not correct.......
Although some etymologist suspect that dead reckoning came from deduced rekoning and this is a common belief, there is no clear history of the term that provides this direct evidence; therefore, dead reckoning is no less correct than ded reckoning. Check the etymology.
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Old 14-02-2011, 16:37   #12
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Where depending on Today's GPS has shown to be a tad off by several hundred yards.
That's not quite technically correct. The GPS is perfectly accurate, unless you have a degraded signal. The problem is that the original charts are out of whack by a significant amount. This is because the original cartographers assumed the earth was a perfect sphere- of course, it isn't. GPS doesn't account for this, whereas the almanac for celestial navigation uses the same (erroneous) data- in this case, two wrongs do make a right.
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Old 15-02-2011, 06:52   #13
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Slocumb was not and old fashioned navigator!

Read the bit in his book (its on the boat note here in the closed bar with wifi - the Caribbean is so far behind the rest of the world!) about sailing up the great Barrier Reef at NIGHT. He was advised not to do so. But he said with 'modern charts' he thought it was quite safe.

Well, guess what we were told when we were doing the same thing 2 years ago? "You CAN'T sail at NIGHT inside the Great Barrier Reef!!!!!"

Both Joshy-babe and we survived

Slocumb would have been the first in the line to buy a GPS if Westmarine had a shop in 1895!


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Old 15-02-2011, 10:37   #14
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Although some etymologist suspect that dead reckoning came from deduced rekoning and this is a common belief, there is no clear history of the term that provides this direct evidence; therefore, dead reckoning is no less correct than ded reckoning. Check the etymology.
Will do. I suppose that if "ded." for "deduced" has no historical basis, then what the heck is "dead" supposed to mean if taken as "assumed" or "derived"?

Because that is what "dead" or "ded" actually would appear to mean.
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Old 15-02-2011, 11:11   #15
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In Elizabethan English 'dead' had also the meaning of absolute; thus dead reckoning, which also dates to 16th century English, had the meaning of finding your way between point A and point B without any means to fix your position other than calculations to take into account deviations from your base line course as affected by wind, tide, current and a ship or boat's hydrodynamic characteristics.
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